Effect of Inlet Clearance on the Aerodynamic Performance of a Centrifugal Blower

Abstract

The present work reports the effect of inlet clearance on the performance of a centrifugal blower, with parallel wall volute, over its full operating range. For a particular impeller configuration, four volutes based on constant angular momentum principle, have been designed and analysed numerically for varying inlet clearances ranging from 0 mm (ideal clearance) to 5 mm. The computational methodology is validated using experimental data. The results indicate that as the clearance increases, the impeller performance in terms of both static and total pressure rise deteriorate. Further, the stage performances deteriorate in terms of efficiency and specific work for all mass flow rates. However, the performance of volute improves at lower mass flow rates compared to the Best Efficiency Point (BEP). A set of correlations have been developed to predict the change in stage performance as a function of clearance ratio. The non-dimensional values of change in specific work, isentropic efficiency and static pressure are found to be same irrespective of the shape of the volute.

Inlet gap effect on aerodynamics and tonal noise generation of a voluteless centrifugal fan

“…Therefore, increasing the gap width worsens the fan performance. The same finding was also clarified in a previous study [12]. However, the anomaly is found in Case 4.…”

Tonal noise of voluteless centrifugal fan generated by turbulence stemming from upstream inlet gap

“…The pressure difference between the fan's inner and outer sides drives air to pass through the gap. As clarified by Hariharan and Govardhan, 12 increasing the gap width worsens the blade aerodynamic performance. According to Lee, 13 the gap gives rise to a local jet that aggravates flow separation near the front shroud.…”

Inlet Gap Effect on Tonal Noise Generated from a Voluteless Centrifugal Fan

“…The pressure difference between the inner and outer sides of the fan drives air to pass through the gap. As clarified by Hariharan and Govardhan [3], increasing the gap width worsens the blade aerodynamic performance.…”

“…The difference in the pressure rise downstream of the fan is only due to the gap design. Hariharan and Govardhan clarified [3] that when the gap width is increased, the blade aerodynamics performance is worsened. In addition, when the gap width is decreased, the performance is improved, which is seen in Figure 6.…”